Analysis of physiological signals can provide clinicians with highly sensitive and accurate indicators to help identify, diagnose and monitor a variety of medical conditions.
The sensing of physiological data such as, for example, cardiac output is of great benefit for the controlled treatment and diagnosis of numerous diseases. Chronically implantable sensors of various types are currently used in treating and monitoring various disease states. Some typical examples of implantable sensors that have been utilized include pressure, oxygen saturation, flow sensors, microphones, intracardiac impedance and similar other implantable medical devices.
There are various externally and internally installed medical devices that monitor physiological signals to provide clinicians accurate information on the medical condition of patients. Under current practice, implanted device sensors are used in conjunction with implanted devices such as pacemakers, defibrillators, neurological stimulators, drug delivery systems and the like. While the functional and technological aspects of these implanted sensors have improved over the years, there remain significant operational and maintenance/reliability problems to overcome. For example, implanted sensors are prone to tissue overgrowth/fibrosis which may limit or interfere with proper/reliable signal acquisition. Similarly, power depletion, current drain, long term signal stability and similar problems associated with chronic use pose various challenges in the successful and long term implementation of implantable sensors.
External sensing systems are also implemented to monitor various vital signs and physiological conditions of a patient. For example, Peripheral Arterial Tone (PAT) is an important signal relating to peripheral vascular responses to automatic nervous system activity. The PAT measures arterial pulse volume changes in the finger tip which may mirror changes or anomalies in automatic nervous system activity and their related vascular events. Other external sensing systems include the finger cuff for blood pressure and the auto-inflating cuff for periodic blood pressure measurement.
One of the advantages of externally implemented sensor over implanted sensors is the option to change, modify or upgrade without an invasive medical procedure on the patient. Further operational efficiency relating to adjustments, maintenance and other conditional adaptability favor external sensors.
Accordingly, there is a need to enable a cooperation between an IMD and external sensors to overcome some of the problems associated with implanted sensors.